One employee was killed and another injured when hot sparks from a welding operation ignited flammable vapors inside a tank in Buffalo, NY, according to OSHA.

The agency has cited the E. I. DuPont De Nemours Co. Yerkes Plant and a contractor in Buffalo for a combined total of 17 serious violations of workplace safety standards as a result of the tragedy, which occurred at the plant in November 2010.

An employee of contractor Mollenberg-Betz Inc. was performing welding atop a 10,000 gallon slurry tank when the explosion occurred, killing him and injuring another Mollenberg-Betz employee. The slurry tank was supposed to be empty but was still connected to two operating slurry tanks, and flammable vapors seeped through the interconnected piping system into the tank on which the employee was working.

"This death and injury graphically underscore how vitally important it is that employers anticipate the hazards associated with welding in potentially explosive atmospheres, and institute all protective measures before allowing such work to begin," said Arthur Dube, OSHA's area director in Buffalo.

OSHA cited both companies for allowing welding to be conducted in an explosive atmosphere; performing welding without disconnecting or blanking the pipelines to the tank; not venting all containers to permit escape of gasses prior to welding; not ensuring that the tanks had been thoroughly cleaned to be absolutely certain that no flammable materials were present; failing to schedule the work so that it would not be conducted during plant operations that might expose combustibles to ignition; and not determining the hazardous areas present or likely to be present in the work location.

Mollenberg-Betz also was cited for not verifying that the slurry tank was empty before welding began and for a lack of specific hazardous energy control procedures. DuPont also was cited for incomplete hazardous energy control procedures; not inserting blanks or blinds in the interconnected slurry tank overflow line to prevent transmission of flammable vapor into the slurry tank; not informing Mollenberg-Betz of potential explosion hazards related to hot work on the slurry tank; not informing Mollenberg-Betz of the plant's hazardous energy control program; and using unapproved electrical equipment in a hazardous location.

DuPont's Yerkes Plant was cited for nine violations with $61,500 in proposed fines while Mollenberg-Betz was cited for eight violations with $55,440 in fines.